Astar, Hidayatul. 2013. “Vowel Variation of Malay Language in The Land of Riau and The Islands of Riau”. Gramatika: Jurnal Ilmiah Kebahasaan Dan Kesastraan 1 (2), 93-102. https://doi.org/10.31813/gramatika/1.2.2013.31.93--102.